FILE - In this July 3, 2018, file photo, referee Mark Geiger shows a yellow card to Colombia's Juan Cuadrado during the round of 16 match between Colombia and England at the 2018 soccer World Cup in Moscow, Russia. Geiger, the first American to referee in the knockout stage of the World Cup, is retiring after 15 seasons in Major League Soccer.(Photo: Victor R. Caivano, AP)

NEW YORK — Mark Geiger looks at the calendar and feels aged out of his job. The first American to referee in the knockout stage of the World Cup is retiring after 15 seasons in Major League Soccer.+

"At 48 when the next World Cup would happen, I didn't think I would be at the same point that I am right now," he said. "The body starts breaking down. And I wouldn't want to go out after a bad tournament."

The Professional Referee Organization, which oversees on-field officials in the United States and Canada, said Wednesday the 44-year-old will become its director of senior match officials. He will lead coaching education for MLS officials and report to former Premier League referee Howard Webb, PRO's general manager.

Geiger has been bothered by his left Achilles tendon. He thinks it is more from wearing soccer cleats than from working in a league that had five stadiums with artificial turf last season.

A former math teacher from Beachwood, New Jersey, Geiger became the second American to referee at two World Cups, after David Socha in 1982 and 1986. Geiger refereed three matches at each of the last two World Cups, including round of 16 matchups between France and Nigeria in 2014, and between England and Colombia last year. He also refereed the 2014 MLS Cup final, three CONCACAF Gold Cups, the 2016 Copa America and the 2012 Olympics and Club World Cup.

He was joined by Jair Marrufo at last year's World Cup, making the U.S. the only nation with two referees at the tournament. But no American has refereed a World Cup match from the quarterfinals on.

"You're always competing with the very best referees from around the world," he said. "The ones from Europe certainly come from higher profile leagues. MLS has made great strides."

Geiger made his MLS debut on May 29, 2004, when Columbus beat visiting San Jose and worked 186 regular-season matches. His on-field finale was Portland's win over San Jose on Nov. 29 in the second leg of the Western Conference final, and he then was an assistant video assistant referee when Real Madrid beat Al-Ain in the Club World Cup final on Dec. 22.

He marvels at how the sport evolved during his time as a referee.

"The game is always going to be fast and quick, but it's getting it's getting faster," he said.